Conventional thermoplastic vulcanizates (TPVs) comprise polypropylene as a continuous phase and crosslinked ethylene propylene diene monomer (EPDM) as a dispersed phase. Using thermoplastic polymers, like polypropylene (PP), as the matrix provides the TPVs with good processability and improved heat resistance, while crosslinked EPDM provides the TPVs with an elastomeric character. Extender oil can be added into the TPV and absorbed into the crosslinked EPDM to adjust hardness. Since most of the components in conventional TPVs are polyolefin-based (non-polar), it is difficult to accommodate polar flame retardant (FR) ingredients in the TPVs. Therefore, it is difficult to achieve a good balance between FR performance and mechanical properties. Compared with polyolefin-based polymers, thermoplastic polyurethane (TPU) is able to accommodate more FR ingredients such as metal hydrates and phosphorous-based FRs. In some applications, TPU together with FR ingredients are used as a FR package for blending with a polyolefin (PO). However, the compatibility between TPU and polyolefins is not good enough, especially when a large amount of FR ingredients are added. To improve compatibility and mechanical properties, commonly used methods include incorporating reactive compatibilizers, such as amine or hydroxyl functionalized POs, into TPU/PO blends. But the effectiveness of this approach is very limited in practice.